Expansible chamber hydraulic cylinders having moveable piston-and-rod assemblies therein are widely used on industrial, earthmoving, and material handling machines and vehicles. It may be advantageous for such a machine or vehicle to include an automatic control system for automatically controlling the extension or retraction of a piston-and-rod assembly within a hydraulic cylinder so that partially or totally automatic work operations may be performed. In one type of automatic control system, a position sensor may be used to determine the position of the piston-and-rod assembly within the cylinder. One challenge with using such a position sensor is creating a robust, accurate, and affordable mount and mounting method for coupling the position sensor with the hydraulic cylinder.
U.S. Pat. No. 5,455,509, issued to Semura et al., discloses a device for mounting a position-detecting sensor to a hydraulic cylinder. Semura discloses a piston rod with a magnetic scale formed on the outer surface thereof and a magnetic sensor mounted on a cylinder head proximate the magnetic scale for detecting the magnetic scale and determining the position of the piston rod. The sensor is mounted on a block, and the block is mounted directly to the head of the cylinder by a plurality of bolts.
Prior sensor-mounting devices and methods for cylinder position sensors may provide complicated assembly operations or may unduly stress components of a cylinder assembly. For example, when a position sensor mount is affixed directly to the head or gland of a cylinder, alignment of the sensor mount (and sensor) with a pattern or detectable feature on the rod may be affected by the alignment (or misalignment) of the head or gland with a detectable feature on the rod. Moreover, bolting or otherwise attaching a sensor mount directly to the head or gland of a cylinder may complicate the required corresponding design or structure of the head or gland, thereby increasing production costs of the gland. Further, when it is desired to retrofit an existing cylinder with a position sensor, attachment of a sensor mount directly to an existing gland, such as by tapping bolt holes in the gland, may not be feasible or possible, for example due to the existing configuration of the gland or the condition of the gland.
The present invention is directed at overcoming one or more problems or disadvantages associated with prior sensor-mounting devices and methods.